Gas-insulated medium- or high-voltage installations, in particular based on the principle of the so-called puffer circuit breaker or self-blast circuit breaker, have an inert, and in particular electrically insulating gas. This insulating gas serves on the one hand for insulating electric currents flowing in the interior of the switch from the housing and on the other hand for extinguishing an arc, in particular in the interior of the switchgear. Sulfur hexafluoride SF6 is usually used for this. SF6 has very good insulating properties and very good arc extinguishing properties, but has a very high greenhouse potential, for which reason use of this insulating gas is in question.
During the extinction of an arc that occurs when the switching contact opens, parts of the SF6 and of the nozzle material decompose, the nozzle generally consisting of polytetrafluoroethylene. These decomposition products generally recombine again after the extinction of the arc and after cooling down, in particular on the surface of the nozzle. In the case of existing switchgear, it has proven to be practicable to combine SF6 as an insulating and extinguishing gas on the one hand and PTFE as a nozzle material on the other hand. When an alternative gas is used, it has however been found to combine unfavorably with the existing nozzle material. Recombination products occur, with adverse effects on the surface of the nozzle and on the functionality of the switchgear. In particular, they are not environmentally friendly because of the fluorine that is bound up in the PTFE.